Titanium Carbide Powder and Titanium Carbide-Ceramics Composite Powder and Method for Production Thereof, and Sintered Compact From the Titanium Carbide Powder and Sintered Compact From the Titanium Carbide/Ceramics Composite Powders and Method for Production Thereof

ABSTRACT

Disclosed is a highly-pure fine titanium carbide powder having a maximum particle size of 100 nm or less and containing metals except titanium in an amount of 0.05 wt % or less and free carbon in an amount of 0.5 wt % or less. The powder has a NaCl-type crystal structure, and a composition represented by TiCxOyNz, wherein X, Y and Z satisfy the relations: 0.5≦X≦1.0; 0≦Y≦0.3; 0≦Z≦0.2; and 0.5≦X+Y+Z≦1.0.) The powder is produced by: dissolving an organic substance serving as a carbon source in a solvent to prepare a liquid, wherein the organic substance contains at least one OH or COOH group which is a functional group coordinatable to titanium of titanium alkoxide, and no element except C, H, N and O; mixing titanium alkoxide with the liquid to satisfy the following relation: 0.7≦α≦1.0 (wherein α is a molar ratio of the carbon source to the titanium alkoxide), so as to obtain a precursor solution; and subjecting a product in the precursor solution to a heat treatment in a non-oxidizing atmosphere or a vacuum atmosphere at a temperature of 1050 to 1500° C. The present invention can provide fine titanium carbide powders with nano-scale particle sizes, which are free of inorganic impurities, such as titanium oxide and metal, low in free carbon, and effective in enhancing characteristics of a titanium carbide-ceramics composite sintered body.

TECHNICAL FIELD

The present invention relates to a titanium carbide powder havingnanometer-scale particle sizes, a titanium carbide-ceramics compositepowder, and the production methods. The present invention also relatesto a sintered body using the titanium carbide powder, a sintered bodyusing the titanium carbide-ceramics composite powder, and the productionmethods.

BACKGROUND ART

In many instances, titanium carbide is used in the form of a compositesintered body. Particularly, a titanium carbide and alumina compositesintered body is used in various applications, such as cutting tools,wear-resistant parts and thin-film magnetic head substrates, based onits excellent characteristics, such as high-temperature strength, heatresistance, wear resistance and chemical resistance.

On the other hand, titanium carbide has a disadvantage of poorsinterability. If titanium carbide is used as a part of a compositematerial to prepare a sintered body, the sintered body is highly likelyto have residual voids or pores. Thus, it is necessary to add asintering aid for increasing the degree of sintering, which leads to aproblem about deterioration in strength of the sintered body.

As means for solving this problem, it is effective to decrease particlesizes of titanium carbide powders in order to improve the sinterability.If a titanium carbide powder is formed to have smaller particle sizes,it will have enhanced sinterability and can be sintered at lowertemperature. This allows a grain growth of ceramics to be effectivelysuppressed during a process of preparing a composite sintered body incombination with ceramics powders. It is known that, when a particlesize of a titanium carbide powder is reduced to 100 nm or less, theabove effect can be significantly enhanced, and additionally thetitanium carbide powder exhibits an excellent dispersion strengtheningeffect in a sintered body.

A titanium carbide powder is widely used as an addition for improvinghigh-temperature hardness and wear-resistant characteristic inWC/Co-based hard metal cutting tools, or as an initial raw material forcermet tools, rolls and dies, in the form of a composite materialcombined with a metal powder, such as a Ni powder.

Recently, in view of particle-size reduction (i.e., micronization ornanonization) of titanium carbide powders which allows a tool to havehigher hardness, higher transverse rupture strength and enhanced wearresistance, a particle-size reduction techniques for titanium carbidepowders become a key challenge.

Heretofore, a titanium carbide powder has been produced by a process ofsubjecting a mixed powder of titanium dioxide (TiO₂) and carbon to aheat treatment in a non-oxidizing atmosphere at a high temperature ofabout 1500° C. to reduce/carbonize the mixed powder, or by a directcarburization process using Ti and TiH₂.

TiC powder produced by the above conventional processes have largeparticle sizes of 1 to 10 μm, and therefore the particle sizes arereduced by ball milling. However, it is difficult to reduce a maximumparticle size to 0.5 μm or less. Moreover, grinding media are inevitablymixed in the powder to cause deterioration in powder quality.

With a view to solving these problems, the following Patent Publication1 discloses a technique of putting a mixed solution of titaniumtetrachloride (TiCl₄) and carbon chloride into a closed containercontaining molten magnesium (Mg) metal under an inert atmosphere,vacuum-separating excess liquid Mg and magnesium chloride (MgCl₂)remaining after a magnesium reduction reaction, and collecting aTiC-base composite from the closed container after the vacuum separationof the liquid Mg and the MgCl₂.

Based on the technique disclosed in the Patent Publication 1, a titaniumcarbide powder can be synthesized at a temperature of 900 to 1000° C.which is lower than ever before. In addition, the obtained titaniumcarbide powder has a fine particle size of 50 nm, and contains freecarbon in a small amount of 0.2 weight %, with a titanium-carbidecrystal structure having a lattice constant of 4.3267 Å which is closeto a theoretical value.

However, the above titanium carbide powder involves a problem about alarge content of impurities, specifically, 0.3 to 0.8 wt % of Mg, 0.1 to0.3 wt % of Cl and 0.1 to 0.6 wt % of Fe.

The following Patent Publication 2 discloses a technique of: the mixtureof water-soluble salt which contains a titanium, one of a metatitanicacid [TiO (OH)₂] slurry or an ultrafine titanium oxide powder, andsolution which dissolved water-soluble metal salt which contains atransition metal in water were prepared as a mixed raw material;spray-drying the mixed raw material to obtain a precursor powder;subjecting the precursor powder to a heat treatment to form an ultrafineTi-transition metal composite oxide powder; mixing nanosized carbonparticles with the ultrafine Ti-transition metal composite oxide powder;drying the mixture to obtain a composite oxide powder; subjecting thecomposite oxide powder to a reduction treatment in a non-oxidizingatmosphere and a carburization heat treatment at 1200 to 1350° C. toproduce a TiC—Co composite powder in which a titanium carbide crystalhas grain sizes of 35 to 81 nm.

Although the technique disclosed in the Patent Publication 2 is designedto set a content of transition metal at 1 wt % or more so that thereduction/carburization heat treatment can be performed at a temperatureof 1350° C. or less to obtain an ultrafine powder, it is difficult toproduce only a highly-pure fine titanium carbide powder in anon-composite form.

Meanwhile, a synthesis of titanium carbide using a liquid phasesynthesis has advantages of being able to stably obtain a fine carbide,and easily mix with other component.

Further, titanium alkoxide used as a titanium source provides anadvantage of allowing a titanium carbide powder with an extremely smallamount of other mixed metal component to be obtained at relatively lowcost.

However titanium carbide powder got by the liquid-phase method reporteduntil now contained free carbon over several wt % or more as impurities,when it was used as a sintering raw material, the free carbon woulddisturb sintering to cause a problem about difficulty in obtaining adense sintered body.

For example, the following Non-Patent Publication 1 discloses atechnique of mixing titanium isopropoxide with several types ofdicarboxylic acids having different chelation properties drying themixture, and subjecting the dried product to a heat treatment in anargon atmosphere containing 0 to 10% of hydrogen to obtain a titaniumcarbide powder. However, the obtained titanium carbide powder containsfree carbon in an amount of 4.2 wt % or more.

As above, no mass production technology has been established that iscapable of producing a titanium carbide powder which has a maximumparticle size of 100 nm or less, and contains free carbon in an amountof 0.5 wt % or less and metals except titanium in a small amount.

In a process of preparing a composite sintered body of titanium carbideand other ceramics including alumina, if a titanium carbide powder as araw material has a smaller particle size, it is more likely to aggregateand thereby cause difficulty in obtaining a sintered body with titaniumcarbide grains homogeneously dispersed therein.

As a technique of solving this problem, in a process of preparing atitanium carbide-dispersed ceramics sintered body, powder particles eachhaving a so-called core-shell structure where a surface of each ceramicsparticle is covered with titanium carbide particles, are effective inpreventing aggregation of a titanium carbide powder so as to obtain thesintered body with a homogenous structure. The core-shell particles arealso effective in suppressing grain growth of ceramics during sintering.

The following Patent Publication 3 discloses one production method forsuch a composite powder. The method disclosed in the Patent Publication3 comprises synthesizing powder particles with a core-shell structurewhere a TiC thin film is formed on a surface of each alumina particle bya CVD (Chemical Vapor Deposition) process, and sintering the powder toobtain a sintered body with titanium carbide grains homogeneouslydispersed therein. However, the CVD process is originally a batchproduction process to be performed in a vacuum apparatus, which isunsuitable for mass production and costly.

-   -   [Patent Publication 1] JP 2005-047739A    -   [Patent Publication 2] JP 2004-323968A    -   [Patent Publication 3] JP 05-270820A    -   [Non-Patent Publication 1] Tom Gallo, Carl Greco, Claude        Peterson, Frank Cambira and Johst Burk, Azko Chemicals Inc.,        Mat. Res. Soc. Symp. Proc. Vol. 271, 1992, pp 887-892

DISCLOSURE OF THE INVENTION Problems that the Invention is to Solve

In view of the above problems in producing a fine titanium carbidepowder having a nanometer-scale particle size, and a sintered body usingthe fine titanium carbide powder, it is an object of the presentinvention to provide a fine titanium carbide powder which is free ofinorganic impurities, such as titanium oxide and metal, low in freecarbon, and effective in enhancing characteristics of a titaniumcarbide-ceramics composite sintered body.

It is another object of the present invention to provide a titaniumcarbide-ceramics composite powder capable of being prepared by mixing aceramics powder, and a fine titanium carbide powder which is free ofinorganic impurities, such as titanium oxide and metal, and low in freecarbon, to allow a titanium carbide-ceramics composite material to berelatively easily obtained.

It is yet another object of the present invention to provide thetitanium carbide-ceramics composite powder in a specific type whichcomprises powder particles with a core-shell structure where a surfaceof each ceramics particle is covered with titanium carbide particles(this composite powder will hereinafter be referred to as “core-shelltype composite powder”).

It is still another object of the present invention to provide asintered body having fine titanium carbide grains homogenously dispersedin a matrix of ceramics, using the titanium carbide-ceramics compositepowder or the core-shell type composite powder.

It is yet still another object of the present invention to provide amethod of producing the fine titanium carbide powder having ananometer-scale particle size, with excellent mass productivity.

It is another further object of the present invention to establishoptimal conditions for mass-producing the titanium carbide powder by aliquid-phase synthesis.

It is still a further object of the present invention to provide amethod of producing the titanium carbide-ceramics composite powder by aliquid-phase synthesis, with excellent mass productivity.

It is an additional object of the present invention to provide a methodof producing the core-shell type composite powder, with excellent massproductivity.

It is yet an additional object of the present invention to establishoptimal conditions for mass-producing the core-shell type compositepowder, by a liquid-phase synthesis.

It is other object of the present invention to provide a method ofproducing the sintered body having fine titanium carbide grainshomogenously dispersed in ceramics, using the titanium carbide-ceramicscomposite powder or the core-shell type composite powder.

Means for Solving the Problems

In order to achieve the above objects, the present invention provides ahighly-pure fine titanium carbide powder which has a maximum particlesize of 100 nm or less, and contains metals except titanium in an amountof 0.05 wt % or less and free carbon in an amount of 0.5 wt % or less.

If the maximum particle size of the titanium carbide powder becomeslarger than 100 nm, the dispersion strengthening effect for suppressinggrain growth in ceramics during a process of producing a sintered bodycannot be sufficiently obtained, and pores will undesirably remain inthe ceramics to cause deterioration in strength of the sintered body.

If metal components as impurities are contained in an amount of largerthan 0.05 wt %, metal components will be changed to a liquid phaseduring the sintering process to form a weak sites which undesirablycause significant deterioration in strength of the sintered body.

If free carbon is contained in the titanium carbide powder, the freecarbon will disturb sintering of the titanium carbide powder during thesintering process to preclude the sintered body from being obtained in adesired density. Moreover, the free carbon causes the occurrence ofpores. In particular, if the free carbon is contained in an amount oflarger than 0.5 wt %, the sintered body will have a relative density ofless than 99% to undesirably cause significant deterioration inmechanical strength of the sintered body.

It is desirable to minimize the content of free carbon in the titaniumcarbide powder. The free carbon content may be reduced by adding/mixinga titanium dioxide (TiO₂) powder to/with the titanium carbide powderobtained by the present invention, and subjecting the mixture to a heattreatment in a non-oxidizing atmosphere to produce a reaction betweenthe titanium dioxide and the free carbon. In this case, the free carbonis removed in such a manner as to be incorporated into the titaniumdioxide as a solid solution or vaporized as CO gas.

Preferably, the titanium carbide powder of the present invention has aNaCl-type crystal structure, and a composition represented by TiCxOyNz,wherein X, Y and Z satisfy the following relations: 0.5≦X≦1.0; 0≦Y≦0.3;0≦Z≦0.2; and 0.5≦X+Y+Z≦1.0. If the titanium carbide powder does notsatisfy the relation “0.5≦X≦1.0”, the NaCl-type crystal structure cannotbe maintained, the powder is not desirable. If Y in the titanium carbidepowder is greater than 0.3, the aforementioned grain-growth suppressingeffect cannot be sufficiently obtained, and a sintered body to beobtained will be adversely effected in terms of heat conductivity andmachinability. If Z in the titanium carbide powder is greater than 0.2,the machinability of the sintered body will be more adversely effectedas compared with oxygen.

The present invention also provides a titanium carbide-ceramicscomposite powder which comprises particles each having a core-shellstructure in which each ceramic particle is covered with particles ofthe above highly-pure fine titanium carbide powder. This core-shell typecomposite powder can suppress grain growth in ceramics during sinteringto facilitate obtaining the titanium carbide-ceramics composite sinteredbody with fine titanium carbide grains homogeneously dispersed in a finestructure of ceramics. In addition, based on the fine dispersion effect,the titanium carbide-ceramics composite sintered body can have a finestructure which has been hardly achievable by conventional productionprocesses, to obtain enhanced strength, fracture toughness and hardness.

When a mixing ratio of the titanium carbide powder to the ceramic powderis set at a high value, it is not possible that all titanium carbidepowder cover respective surfaces of the ceramic particles. Specifically,a part of the titanium carbide powder particles cover respectivesurfaces of the ceramic particles, and the remaining titanium carbidepowder particles are dispersed in a matrix of the ceramics. Thus, thistitanium carbide-ceramics composite powder (hereinafter referred to as“dispersion type composite powder) can have the same fine dispersioneffect as that of the above core-shell type composite powder.

In the above titanium carbide-ceramics composite material (i.e.,core-shell type and dispersion type composite powders, titaniumcarbide-coated alumina powders are suitably used in a wide range ofapplications, such as cutting tools, wear-resistant parts and thin-filmmagnetic head substrates.

Further, the present invention provides a method of producing thehighly-pure fine titanium carbide powder which has a maximum particlesize of 100 nm or less and contains metals except titanium in an amountof 0.05 wt % or less and free carbon in an amount of 0.5 wt % or less.The method comprises the steps of: dissolving an organic substanceserving as a carbon source in a solvent to prepare a liquid, wherein theorganic substance contains at least one OH or COOH group which is afunctional group coordinatable to titanium of titanium alkoxide, and noelement except C, H, N and O; mixing titanium alkoxide with the liquidto satisfy the following relation: 0.7≦α≦1.0 (wherein α is a molar ratioof the carbon source to the titanium alkoxide), so as to obtain asolution, i.e., a precursor solution; drying the precursor solutionaccording to need to obtain a product; and subjecting the product to aheat treatment in a non-oxidizing atmosphere or a vacuum atmosphere at atemperature of 1050 to 1500° C.

In the above method, the organic substance having ligands coordinatableto titanium of titanium alkoxide is used as the carbon source tosubstitute the functional group of the carbon source for ligandsexisting in the titanium alkoxide so as to provide a molecularlyhomogenous composition of the carbon source and the titanium source.This homogenous composition makes it possible to allow a temperature ofa subsequent carbonization reaction to be drastically lowered, so thatthe growth of the titanium carbide particles can be suppressed to obtainfine particles having a maximum particle size of 100 nm or less.

In the liquid phase reaction, catalyst containing metal is not used andhigh-purity titanium alkoxide is used as titanium source. Thus, anamount of metal impurities can be limited to 0.05 wt % or less.

In the molecularly homogenous composition of the carbon source and thetitanium source, the carbon source does not exist locally, and thereforean amount of carbon source never becomes insufficient for the titaniumsource. Thus, except titanium carbide, any substance, such as titaniumoxide, will not be produced.

When an amount of titanium alkoxide to be mixed with the liquid preparedby dissolving the organic substance serving as a carbon source in asolvent is appropriately set in the above manner, a titanium carbidematerial containing free carbon in an amount of 0.5 wt % or less can beobtained. For example, if the mixing ratio of the carbon source to thetitanium source is set at an excessively high value, a large amount offree carbon will be undesirably produced. If the mixing ratio of thecarbon source to the titanium source is set at an excessively low value,a substance other than a titanium carbide group will be undesirablyproduced.

The functional group of the carbon source comprises OH group or COOHgroup which capable of easily forming a coordinate bond. For example,the carbon source includes: phenols including phenol and catechol;novolac-type phenolic resin; organic acid including salicylic acid,phthalic acid, catechol and anhydrous citric acid; andethylenediaminetetraacetic acid (EDTA). These organic compounds may beused independently or may be used as a combination of two or more ofthem. However, the use of a carbon source containing an element otherthan C, H, N and O is undesirable, because such an element is likely tobe left as impurities.

In view of reducing a maximum particle size to 100 nm or less, thecarbonization temperature is set in the range of 1050 to 1500° C. If thecarbonization temperature is below 1050° C., a time required forcarbonization will be excessively extended to cause deterioration inproductivity. If the carbonization temperature is above 1500° C., thegrowth of titanium carbide particles will be significantly accelerated,and finally the maximum particle size will be increased up to largerthan 100 nm.

Preferably, an organic substance having two or more ligands and a cycliccompound. is used as the carbon source. When the ligand is two or moremultidentate ligands, the carbon source can form chelate bonds totitanium so as to be stronger coordinated to the titanium as comparedwith a compound with a unidentate ligand. Thus, the carbon source can behighly homogenously mixed with the titanium source without unevendistribution. This is effective in reducing the amount of free carbon.In addition, the cyclic compound has a high carbon ratio which remainsas carbon after the heat treatment, and therefore allows a requiredamount of carbon source to be reduced so as to contribute to effectivereduction in cost.

Even after the precursor solution is heated and dried, the carbon sourcefirmly coordinatable to titanium can maintain the coordination state.Thus, in the product, the carbon source is highly homogenously mixedwith the titanium source without uneven distribution, and the amount offree carbon is effective reduced.

Preferably, the titanium alkoxide serving as the titanium sourceincludes titanium (IV) methoxide, titanium (IV) ethoxide, titanium (IV)isopropoxide and titanium (IV) butoxide. Among them, the titanium (IV)isopropoxide is particularly preferable in view of cost andhandleability.

The production method for the fine titanium carbide powder can beapplied to a method of producing a mixed powder with a ceramic powder,such as alumina, other oxide, nitride or boride.

In this case, ceramics powders are mixed with a precursor solution whichis a molecularly homogenous composition of carbon source and titaniumsource, to slurry the precursor solution. Then, organic solvent isremoved from the slurry to obtain a core-shell type powder where asurface of each ceramic particle is covered with a product obtained bydrying the precursor solution, or a dispersion type composite powder.Then, the core-shell type or dispersion type composite powder issubjected to a heat treatment in a non-oxidizing atmosphere or a vacuumatmosphere.

In this production method, a molar ratio “a” of the carbon source to thetitanium alkoxide is set to satisfy the following relation: 0.75≦α≦1.1,so as to obtain a titanium carbide-ceramics composite powder containingfree carbon in an amount of 0.5 wt % or less. That is, the molar ratioof the carbon source to the titanium alkoxide is required to be set at avalue higher than that in the production method for only the titaniumcarbide. The reason is that the ceramic powder slightly disturbs thecarbonization reaction in the homogenous composition of the carbonsource and the titanium source.

The core-shell type or dispersion type composite powder can be subjectedto a hot pressing process in a vacuum atmosphere or a nitrogen or argonatmosphere, at a press temperature of 1400 to 1850° C. and a presspressure of 10 to 50 MPa, so as to obtain a fine titaniumcarbide-dispersed ceramic sintered body suppressed grain growth.

If the press temperature is below 1400° C., the composite powder willnot be sufficiently sintered to cause undesirable residual pores. If thepress temperature is above 1850° C., the grain-growth suppressing effectwill not be obtained to cause grain growth of ceramic.

If the press pressure is lower than 10 MPa, the composite powder willnot be sufficiently sintered to cause undesirable residual pores. If thepress pressure is higher than 50 MPa, the need for increasing thestrength of a mold and/or a punch will undesirably arise.

Alternatively, the core-shell type or dispersion type composite powdermay be formed into a powder compact, and the powder compact may besintered in a vacuum atmosphere or a nitrogen or argon atmosphere, at atemperature of 1500 to 1900° C.

If the sintering temperature is below 1500° C., the composite powderwill not be sufficiently sintered to cause undesirable residual pores.If the sintering temperature is above 1900° C., the grain-growthsuppressing effect will not be obtained to cause grain growth ofceramic.

The titanium carbide-ceramics composite sintered body obtained bysubjecting the core-shell type or dispersion type composite powder tothe hot pressing process or the forming/sintering process to have arelative density of 95% or more may further be subjected to a hotisostatic pressing (HIP) process in a nitrogen or argon atmosphere, at atemperature of 1400 to 1600° C. and a pressure of 50 to 200 Mpa, so asto obtain a fine titanium carbide-dispersed ceramic sintered bodywithout residual pores.

If the HIP temperature is below 1400° C., an HIP effect will not besufficiently obtained to cause undesirable residual pores. If the HIPtemperature is above 1600° C., the grain-growth suppressing effect willnot be obtained to cause grain growth of ceramic.

If the HIP pressure is lower than 50 MPa, the HIP effect will not besufficiently sintered to cause undesirable residual pores. If the HIPpressure is higher than 200 MPa, the need for increasing the strength ofan HIP apparatus will undesirably arise.

In the method of producing the fine titanium carbide-dispersed ceramicsintered body, it is not essential to once dry the slurry obtained bymixing a ceramic powder with the precursor solution which is a mixedsolution of the carbon source, the organic solvent and the titaniumalkoxide. That is, the slurry may be solidified through gelation, andthe solidified product may be subjected to a carbonization andsintering.

EFFECT OF THE INVENTION

As above, in the present invention, a liquid-phase synthesis havingexcellent mass productivity as compared with a gas-phase synthesis isemployed as means for synthesizing a fine titanium carbide powder havinga nanometer-scale particle size. By replacing the ligand/ligands of thetitanalkoxide with functional group/groups of carbon source in theliquid phase, this makes stable coordination state so as to preventformation of titanium oxides and mixing of other metal components asimpurities.

An amount of free carbon which is not bonded to titanium can besignificantly reduced by controlling a structure and amount of thefunctional group of the carbon source, and a substitution reactionbetween the functional group/groups and the ligand/ligands of titaniumsource.

Titanium and carbon are bonded to each other on a molecular level. Thus,the carbonization reaction can be performed at a drastically loweredtemperature to suppress growth of the titanium carbide particles so asto obtain a fine high-quality titanium carbide powder.

The production method for the fine highly-pure titanium carbide powdercan be applied to the production of a titanium carbide-ceramic compositepowder so as to obtain a core-shell type composite powder. Thiscore-shell type composite powder can be sintered while suppressing graingrowth of ceramic to obtain a titanium carbide-dispersed high-densitysintered body optimally usable in cutting tools, wear-resistant parts,thin-film magnetic head substrates or the like.

Particularly, in the titanium carbide-dispersed alumina-based compositematerial using the titanium carbide powder having a maximum particlesize of 100 nm or less of the present invention, based on thegrain-growth suppressing effect of the titanium carbide particles inalumina matrix, alumina crystals has smaller grain sizes than everbefore, to facilitate sintering even in contact points with titaniumcarbide particles so as to prevent the occurrence of micro pores.

The sintered body having such a nanostructure has excellentmachinability for mirror like finishing to facilitate obtaining anoptical mirror surface (Rtm: 5 nm or less), and allows a polishing rateto be increased so as to contribute to increase in productionefficiency. Further, this sintered body can obtain excellent surfaceroughness through ion machining (reactive ion etching or ion beametching).

The sintered body is excellent in strength and fracture toughness(resistance to crack formation/propagation), and free of the occurrenceof cracks and the pull-out of particles during machining. The sinteredbody is also excellent in terms of purity, and optimally usable as amaterial of thin-film magnetic head substrates. In a thin-film magnetichead using this sintered body, machining conditions in a productionprocess thereof can be optimized to suppress the occurrence of cracksand the pull-out of particles at an end of a thin-film magnetic headslider so as to ensure high reliability as a thin-film magnetic head.

The sintered body of the present invention has fine titanium carbidegrains. Thus, even if a content of titanium carbide is in the range of10 to less than 30 wt % which is less than that (30 to 40 wt %) of aconventional substrate material, mechanical and machining propertiesequivalent or superior to those of the conventional substrate materialcan be obtained to ensure reduction in weight and increase in heatconductivity of the thin-film magnetic head slider.

BEST MODE FOR CARRYING OUT THE INVENTION

An embodiment of the present invention will now be described based onexamples.

EXAMPLE 1

20 g of salicylic acid having a molecular mass of 138.1 serving as acarbon source was added to 60 ml of 2-methoxyethanol serving as asolvent, and the mixture was stirred to dissolve the carbon source inthe solvent so as to obtain transparent and colorless liquid serving asraw material of precursor.

46.4 g of titanium isopropoxide which has titanium content of about 7.8g and molecular mass of 284.2, and is in liquid form at roomtemperature, was added to the liquid, and the mixture was stirred toobtain a highly-transparent homogenous reddish brown composition havingsalicylic acid substituted and coordinated for/to a part of titaniumisopropoxide. The mixture was successively stirred for 2 hours, and thenheated with stirring in an oil bath to obtain a dried product. Thisdried product has an orange color, and a molar ratio “α” of salicylicacid serving as a carbon source to titanium isopropoxide serving as atitanium source of 0.9.

Then, in a graphite crucible having an inner diameter of 200 mm and aheight of 80 mm, the obtained dried product was subjected to a heattreatment which comprises heating the dried product up to a maximumtreatment temperature of 1050 to 1500° C. under a vacuum atmosphere of13.33 Pa (0.1 Torr), holding the maximum treatment temperature for 4hours, and naturally cooling the heated product, to obtain acomposition.

FIG. 1 shows an X-ray powder diffraction measurement result on thecomposition obtained at a treatment temperature of 1350° C.

In view of the result, it was clear that the obtained composition issingle-phase titanium carbide without containing crystalline impurities,such as titanium oxide. The synthesized titanium carbide has a latticeconstant of 4.327 Å.

FIG. 2 shows a transmission electron microscope (TEM) photograph of theobtained titanium carbide powder. Based on the photograph, it was proventhat the titanium carbide powder has a maximum particle size of 100 nmor less. As a result of measurement based on acarbon-sedimentation/separation/combustion/infrared adsorptionspectroscopy, a content of free carbon in the obtained titanium carbidepowder was 0.07 wt %.

As a result of measurement based on a calibration curve method influorescent X-ray spectroscopy, an amount of metal except titanium, inthe obtained titanium carbide powder, was 0.02 wt %.

EXAMPLE 2

62 g of salicylic acid serving as a carbon source was added to 170 ml of2-methoxyethanol serving as solvent, and the mixture was stirred todissolve the carbon source in the solvent so as to obtain a transparentand colorless liquid serving as raw material of precursor.

130 g of titanium isopropoxide which has titanium content of about 22 gand is in liquid form at room temperature, was added to the liquid, andthe mixture was stirred to obtain a highly-transparent homogenousreddish brown composition having salicylic acid substituted andcoordinated for/to a part of titanium isopropoxide. The mixture wassuccessively stirred for 2 hours, and then 46 g of alumina powder wasadded to the mixture. The obtained mixture was stirred using a stirrerfor 3 hours, and then heated with stirring in an oil bath to obtain adried product. This dried product has an orange color, and a molar ratio“a” of salicylic acid serving as the carbon source to titaniumisopropoxide serving as a titanium source of 1.0.

Then, in a graphite crucible having an inner diameter of 200 mm and aheight of 80 mm, the obtained dried product was subjected to a heattreatment which comprises heating the dried product up to a maximumtreatment temperature of 1050 to 1500° C. under a vacuum atmosphere of13.33 Pa (0.1 Torr), holding the maximum treatment temperature for 4hours, and naturally cooling the heated product, to obtain acomposition.

FIG. 3 shows an X-ray powder diffraction measurement result on thecomposition obtained at a treatment temperature of 1350° C.

In view of the result, it was clear that the obtained compositionconsists only of titanium carbide and alumina without containingcrystalline impurities, such as titanium oxide. The synthesized titaniumcarbide has a lattice constant of 4.329 Å.

FIG. 4 shows a transmission electron microscope (TEM) photograph of theobtained titanium carbide-alumina composite powder. Based on thephotograph, it was proven that an alumina particle was covered withtitanium carbide particles, and the titanium carbide particles have amaximum particle size of 100 nm or less. As a result of measurementbased on a carbon-sedimentation/separation/combustion/infraredadsorption spectroscopy, a ratio of free carbon to titanium carbide inthe obtained composition was 0.03 wt %.

EXAMPLE 3

The titanium carbide-covered alumina powder obtained in Example 2 wasput in a carbon mold, and subjected to a hot pressing process under anargon atmosphere at a press pressure of 25 MPa and a press temperatureof 1800° C. for 90 minutes, to obtain a sintered body having a length of50 mm, a width of 50 mm and a thickness of 4 mm. A density of thesintered body was measured by an Archimedes' method. As a result, it wasproven that the sintered body has a density of 4.27×10³ kg/m³, and arelative density of 99.5%.

Then, the sintered body was subjected to surface polishing, and thensubjected to mirror-like finishing based on lapping using a tin plate.The finished sintered body was observed using a scanning electronmicroscope (SEM).

FIG. 5 shows a SEM photograph of a mirror-finished surface of theobtained alumina-titanium carbide composite sintered body. As seen inthis photograph, titanium carbide particles are homogenously distributedin the sintered alumina. In addition, any pore due to free carbon andother was not observed.

Table 1 shows a comparison between inventive samples and comparativesamples. In the comparative samples 1 and 3, the molar ratio “a” of thecarbon source to the titanium source is not set at an adequate value,which results in an extremely large amount of free carbon. In thecomparative samples 2 and 4, the molar ratio “a” of the carbon source tothe titanium source is not set at an adequate value, and thereby no TiCphase is observed.

TABLE 1 Maximun Particle Color of Carbon Source/ Presence Addition ofLattice Size of TiC Free Carbon Carbon Precursor Color of Dried TitaniumSource of TiC Alumina Constant based on TEM Amount Source SolutionPowder (Molar Ratio) α Phase Powder of TiC Observation (nm) (wt %)Inventive salicylic reddish brown orange 0.9 YES NO 4.327 40 0.07 Sample1 acid Inventive salicylic reddish brown orange 1.0 YES YES 4.329 400.03 Sample 2 acid Inventive salicylic reddish brown orange 1.0 YES NO4.327 60 0.1 Sample 4 acid Inventive salicylic orange orange-yellow 0.70YES NO 4.310 50 0.06 Sample 5 acid Inventive salicylic reddish brownorange 1.1 YES YES 4.329 55 0.05 Sample 6 acid Inventive salicylicorange orange-yellow 0.75 YES YES 4.325 50 0.03 Sample 7 acidComparative salicylic reddish brown orange 1.1 YES NO 4.327 65 0.96Sample 1 acid Comparative salicylic yellow yellow 0.55 NO NO — — —Sample 2 acid Comparative salicylic reddish brown orange 1.2 YES YES4.325 60 0.92 Sample 3 acid Comparative salicylic yellow yellow 0.55 NOYES — — — Sample 4 acid

For reference, Table 2 shows one example of relative densities ofsintered bodies obtained by subjecting inventive titaniumcarbide-covered alumina powders different in free carbon amount to a hotpressing process under an argon atmosphere at a press pressure of 30 MPaand a press temperature of 1800° C. for 90 minutes.

TABLE 2 Free Carbon Relative Amount (wt %) Density (%) 0.1 99.4 0.3 99.30.5 99.0 0.7 98.1 1.0 97.3

Table 3 shows one example of particle sizes of inventive titaniumcarbide-covered alumina powders different in X, Y and Z values of thetitanium carbide TiCxOyNz, and heat conductivities of sintered bodiesobtained by subjecting the respective powders to the hot pressingprocess.

TABLE 3 Particle Heat Conductivity X Y Size (nm) (W/m · k) 0.9 0.1 2024.0 0.8 0.2 30 23.6 0.7 0.3 70 22.1 0.6 0.4 110 20.1 0.5 0.5 130 18.4

Note) Respective values of X and Y was set as shown in Table 3, whereinZ=0.

-   -   The values of X, Y and Z were determined based on C analysis        (infrared absorption method), N and O analysis and an X-ray        diffraction method.

Table 4 shows one example of cutting loads of sintered bodies obtainedby subjecting inventive titanium carbide-covered alumina powdersdifferent in X, Y and Z values of the titanium carbide TiCxOyNz, to thehot pressing process, wherein the cutting load means a load of a diamondblade used for cutting each of the obtained sintered bodies.

TABLE 4 X Z Cutting Load (W) 1 0 200 0.9 0.1 230 0.8 0.2 270 0.7 0.3 3500.5 0.5 450

Note) Respective values of X and Z was set as shown in Table 4, whereinY=0.

-   -   The values of X, Y and Z were determined based on C analysis        (infrared absorption method), N and O analysis and an X-ray        diffraction method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing an X-ray diffraction pattern of a titaniumcarbide powder produced by a method of the present invention.

FIG. 2 is a transmission electron microscope photograph of a titaniumcarbide powder produced by a method of the present invention.

FIG. 3 is a graph showing an X-ray diffraction pattern of a titaniumcarbide-covered alumina powder produced by a method of the presentinvention.

FIG. 4 is a transmission electron microscope photograph of a titaniumcarbide-covered alumina powder produced by a method of the presentinvention.

FIG. 5 is a scanning electron microscope photograph of a titaniumcarbide-alumina composite sintered body produced by a method of thepresent invention.

1. Highly-pure fine titanium carbide powders which have a maximumparticle size of 100 nm or less, and contain metals except titanium inan amount of 0.05 wt % or less and free carbon in an amount of 0.5 wt %or less.
 2. The highly-pure fine titanium carbide powder as defined inclaim 1, which comprises titanium carbide having a NaCl-type crystalstructure, and a composition represented by TiCxOyNz, wherein X, Y and Zsatisfy the following relations: 0.5≦X≦1.0; 0≦T≦0.3; 0≦Z≦0.2; and0.5≦X+Y+Z≦1.0.
 3. Titanium carbide-ceramics composite powders whichcomprise particles each having a core-shell structure in which a ceramicparticle is covered with particles of the highly-pure fine titaniumcarbide powder as defined in claim 1 or
 2. 4. Titanium carbide-ceramicscomposite powders which comprise a part of the high-pure and finetitanium carbide powders as defined in claim 1 or 2 cover the ceramicpowder, and remaining titanium carbide powder particles are dispersed inmatrix of ceramic particles.
 5. The titanium carbide-ceramics compositepowder as defined in claim 3, wherein said ceramic particles arealumina.
 6. A method of producing the highly-pure fine titanium carbidepowder as defined in claim 1 or 2, comprising the steps of: dissolvingan organic substance serving as a carbon source in a solvent to preparea liquid, said organic substance containing at least one OH or COOHgroup which is a functional group coordinatable to titanium of titaniumalkoxide, and no element except C, H, N and O; mixing titanium alkoxidewith said liquid to satisfy the following relation: 0.7≦α≦1.0 (wherein αis a molar ratio of said carbon source to said titanium alkoxide), so asto obtain a precursor solution; solidifying said precursor solution toobtain a product; and subjecting said product to a heat treatment in anon-oxidizing atmosphere or a vacuum atmosphere at a temperature of 1050to 1500° C.
 7. The method as defined in claim 6, wherein said carbonsource is one selected from the group consisting of: phenols includingphenol and catechol; novolac-type phenolic resin; organic acid includingsalicylic acid, phthalic acid, catechol and anhydrous citric acid; andEDTA.
 8. The method as defined in claim 6, wherein said carbon sourcehas two or more ligands, and a cyclic compound.
 9. The method as definedin claim 6, wherein said carbon source in said product obtained in saidsolidifying step is coordinated to titanium of said titanium alkoxide.10. The method as defined in claim 6, wherein said titanium alkoxide isone selected from the group consisting of titanium (IV) methoxide,titanium (IV) ethoxide, titanium (IV) isopropoxide and titanium (IV)butoxide.
 11. A method of producing the titanium carbide-ceramicscomposite powder as defined in claim 3, comprising the steps of:dissolving an organic substance serving as a carbon source in a solventto prepare a liquid; mixing titanium alkoxide with said liquid tosatisfy the following relation: 0.75≦α≦1.1 (wherein α is a molar ratioof said carbon source to said titanium alkoxide), so as to obtain aprecursor solution; mixing a ceramics powder with said precursorsolution to slurry said precursor solution; solidifying said slurriedprecursor solution to obtain a product; and subjecting said product to aheat treatment in a non-oxidizing atmosphere or a vacuum atmosphere at atemperature of 1050 to 1500° C.
 12. The method as defined in claim 11,wherein said carbon source is one selected from the group consisting of:phenols including phenol and catechol; novolac-type phenolic resin;organic acid including salicylic acid, phthalic acid, catechol andanhydrous citric acid; and EDTA.
 13. The method as defined in claim 11,wherein said carbon source has two or more ligands, and a cycliccompound.
 14. The method as defined in claim 11, wherein said carbonsource in said product obtained in said solidifying step is coordinatedto titanium of said titanium alkoxide.
 15. The method as defined inclaim 11, wherein said titanium alkoxide is one selected from the groupconsisting of titanium (IV) methoxide, titanium (IV) ethoxide, titanium(IV) isopropoxide and titanium (IV) butoxide.
 16. The method as definedin claim 11, wherein said ceramics powders are alumina.
 17. A titaniumcarbide sintered body obtained from the highly-pure fine titaniumcarbide powder as defined in claim 1 or
 2. 18. A method of producing atitanium carbide sintered body, comprising the step of subjecting thehighly-pure fine titanium carbide powder obtained by the method asdefined in claim 6, to a hot pressing process in a vacuum atmosphere ora nitrogen or argon atmosphere, at a press temperature of 1400 to 1850°C. and a press pressure of 10 to 50 MPa.
 19. A method of producing atitanium carbide sintered body, comprising the steps of: forming thehighly-pure fine titanium carbide powder obtained by the method asdefined in claim 6, into a powder compact; and sintering said powdercompact in a vacuum atmosphere or a nitrogen or argon atmosphere, at atemperature of 1500 to 1900° C.
 20. The method as defined in claim 18,which further includes the step of subjecting said titanium carbidesintered body to a hot isostatic pressing (HIP) process in a nitrogen orargon atmosphere, at a temperature of 1400 to 1600° C. and a pressure of50 to 200 MPa.
 21. A titanium carbide-ceramics composite sintered bodyobtained from the titanium carbide-ceramics composite powder as definedin claim
 3. 22. A method of producing a titanium carbide-ceramicscomposite sintered body, comprising the step of subjecting the titaniumcarbide-ceramics composite powder obtained by the method as defined inclaim 11, to a hot pressing process in a vacuum atmosphere or a nitrogenor argon atmosphere, at a press temperature of 1400 to 1850° C. and apress pressure of 10 to 50 MPa.
 23. A method of producing a titaniumcarbide-ceramics composite sintered body, comprising the steps of:forming the titanium carbide-ceramics composite powder obtained by themethod as defined in claim 11, into a powder compact; and sintering saidpowder compact in a vacuum atmosphere or a nitrogen or argon atmosphere,at a temperature of 1500 to 1900° C.
 24. The method as defined in claim22, which further includes the step of subjecting said titaniumcarbide-ceramics composite sintered body to a hot isostatic pressing(HIP) process in a nitrogen or argon atmosphere, at a temperature of1400 to 1600° C. and a pressure of 50 to 200 MPa.
 25. The titaniumcarbide-ceramics composite powder as defined in claim 4, wherein saidceramic particles are alumina.
 26. A method of producing the titaniumcarbide-ceramics composite powder as defined in claim 4, comprising thesteps of: dissolving an organic substance serving as a carbon source ina solvent to prepare a liquid; mixing titanium alkoxide with said liquidto satisfy the following relation: 0.75≦α≦1.1 (wherein α is a molarratio of said carbon source to said titanium alkoxide), so as to obtaina precursor solution; mixing a ceramics powder with said precursorsolution to slurry said precursor solution; solidifying said slurriedprecursor solution to obtain a product; and subjecting said product to aheat treatment in a non-oxidizing atmosphere or a vacuum atmosphere at atemperature of 1050 to 1500° C.
 27. A method of producing the titaniumcarbide-ceramics composite powder as defined in claim 5, comprising thesteps of: dissolving an organic substance serving as a carbon source ina solvent to prepare a liquid; mixing titanium alkoxide with said liquidto satisfy the following relation: 0.75≦α≦1.1 (wherein α is a molarratio of said carbon source to said titanium alkoxide), so as to obtaina precursor solution; mixing a ceramics powder with said precursorsolution to slurry said precursor solution; solidifying said slurriedprecursor solution to obtain a product; and subjecting said product to aheat treatment in a non-oxidizing atmosphere or a vacuum atmosphere at atemperature of 1050 to 1500° C.
 28. The method as defined in claim 4,wherein said carbon source has two or more ligands, and a cycliccompound.
 29. The method as defined in claim 4, wherein said carbonsource in said product obtained in said solidifying step is coordinatedto titanium of said titanium alkoxide.
 30. The method as defined inclaim 4, wherein said titanium alkoxide is one selected from the groupconsisting of titanium (IV) methoxide, titanium (IV) ethoxide, titanium(IV) isopropoxide and titanium (IV) butoxide.
 31. The method as definedin claim 4, wherein said ceramics powders are alumina.
 32. The method asdefined in claim 5, wherein said carbon source has two or more ligands,and a cyclic compound.
 33. The method as defined in claim 5, whereinsaid carbon source in said product obtained in said solidifying step iscoordinated to titanium of said titanium alkoxide.
 34. The method asdefined in claim 5, wherein said titanium alkoxide is one selected fromthe group consisting of titanium (IV) methoxide, titanium (IV) ethoxide,titanium (IV) isopropoxide and titanium (IV) butoxide.
 35. The method asdefined in claim 5, wherein said ceramics powders are alumina.
 36. Amethod of producing a titanium carbide sintered body, comprising thestep of subjecting the highly-pure fine titanium carbide powder obtainedby the method as defined in claim 7, to a hot pressing process in avacuum atmosphere or a nitrogen or argon atmosphere, at a presstemperature of 1400 to 1850° C. and a press pressure of 10 to 50 MPa.37. A method of producing a titanium carbide sintered body, comprisingthe step of subjecting the highly-pure fine titanium carbide powderobtained by the method as defined in claim 8, to a hot pressing processin a vacuum atmosphere or a nitrogen or argon atmosphere, at a presstemperature of 1400 to 1850° C. and a press pressure of 10 to 50 MPa.38. A method of producing a titanium carbide sintered body, comprisingthe step of subjecting the highly-pure fine titanium carbide powderobtained by the method as defined in claim 9, to a hot pressing processin a vacuum atmosphere or a nitrogen or argon atmosphere, at a presstemperature of 1400 to 1850° C. and a press pressure of 10 to 50 MPa.39. A method of producing a titanium carbide sintered body, comprisingthe step of subjecting the highly-pure fine titanium carbide powderobtained by the method as defined in claim 10, to a hot pressing processin a vacuum atmosphere or a nitrogen or argon atmosphere, at a presstemperature of 1400 to 1850° C. and a press pressure of 10 to 50 MPa.40. A method of producing a titanium carbide sintered body, comprisingthe steps of: forming the highly-pure fine titanium carbide powderobtained by the method as defined in claim 7, into a powder compact; andsintering said powder compact in a vacuum atmosphere or a nitrogen orargon atmosphere, at a temperature of 1500 to 1900° C.
 41. A method ofproducing a titanium carbide sintered body, comprising the steps of:forming the highly-pure fine titanium carbide powder obtained by themethod as defined in claim 8, into a powder compact; and sintering saidpowder compact in a vacuum atmosphere or a nitrogen or argon atmosphere,at a temperature of 1500 to 1900° C.
 42. A method of producing atitanium carbide sintered body, comprising the steps of: forming thehighly-pure fine titanium carbide powder obtained by the method asdefined in claim 9, into a powder compact; and sintering said powdercompact in a vacuum atmosphere or a nitrogen or argon atmosphere, at atemperature of 1500 to 1900° C.
 43. A method of producing a titaniumcarbide sintered body, comprising the steps of: forming the highly-purefine titanium carbide powder obtained by the method as defined in claim10, into a powder compact; and sintering said powder compact in a vacuumatmosphere or a nitrogen or argon atmosphere, at a temperature of 1500to 1900° C.
 44. The method as defined in claim 19, which furtherincludes the step of subjecting said titanium carbide sintered body to ahot isostatic pressing (HIP) process in a nitrogen or argon atmosphere,at a temperature of 1400 to 1600° C. and a pressure of 50 to 200 MPa.45. A titanium carbide-ceramics composite sintered body obtained fromthe titanium carbide-ceramics composite powder as defined in claim 4.46. A titanium carbide-ceramics composite sintered body obtained fromthe titanium carbide-ceramics composite powder as defined in claim 5.47. A method of producing a titanium carbide-ceramics composite sinteredbody, comprising the step of subjecting the titanium carbide-ceramicscomposite powder obtained by the method as defined in claim 12, to a hotpressing process in a vacuum atmosphere or a nitrogen or argonatmosphere, at a press temperature of 1400 to 1850° C. and a presspressure of 10 to 50 MPa.
 48. A method of producing a titaniumcarbide-ceramics composite sintered body, comprising the step ofsubjecting the titanium carbide-ceramics composite powder obtained bythe method as defined in claim 13, to a hot pressing process in a vacuumatmosphere or a nitrogen or argon atmosphere, at a press temperature of1400 to 1850° C. and a press pressure of 10 to 50 MPa.
 49. A method ofproducing a titanium carbide-ceramics composite sintered body,comprising the step of subjecting the titanium carbide-ceramicscomposite powder obtained by the method as defined in claim 14, to a hotpressing process in a vacuum atmosphere or a nitrogen or argonatmosphere, at a press temperature of 1400 to 1850° C. and a presspressure of 10 to 50 MPa.
 50. A method of producing a titaniumcarbide-ceramics composite sintered body, comprising the step ofsubjecting the titanium carbide-ceramics composite powder obtained bythe method as defined in claim 15, to a hot pressing process in a vacuumatmosphere or a nitrogen or argon atmosphere, at a press temperature of1400 to 1850° C. and a press pressure of 10 to 50 MPa.
 51. A method ofproducing a titanium carbide-ceramics composite sintered body,comprising the step of subjecting the titanium carbide-ceramicscomposite powder obtained by the method as defined in claim 16, to a hotpressing process in a vacuum atmosphere or a nitrogen or argonatmosphere, at a press temperature of 1400 to 1850° C. and a presspressure of 10 to 50 MPa.
 52. A method of producing a titaniumcarbide-ceramics composite sintered body, comprising the steps of:forming the titanium carbide-ceramics composite powder obtained by themethod as defined in claim 12, into a powder compact; and sintering saidpowder compact in a vacuum atmosphere or a nitrogen or argon atmosphere,at a temperature of 1500 to 1900° C.
 53. A method of producing atitanium carbide-ceramics composite sintered body, comprising the stepsof: forming the titanium carbide-ceramics composite powder obtained bythe method as defined in claim 13, into a powder compact; and sinteringsaid powder compact in a vacuum atmosphere or a nitrogen or argonatmosphere, at a temperature of 1500 to 1900° C.
 54. A method ofproducing a titanium carbide-ceramics composite sintered body,comprising the steps of: forming the titanium carbide-ceramics compositepowder obtained by the method as defined in claim 14, into a powdercompact; and sintering said powder compact in a vacuum atmosphere or anitrogen or argon atmosphere, at a temperature of 1500 to 1900° C.
 55. Amethod of producing a titanium carbide-ceramics composite sintered body,comprising the steps of: forming the titanium carbide-ceramics compositepowder obtained by the method as defined in claim 15, into a powdercompact; and sintering said powder compact in a vacuum atmosphere or anitrogen or argon atmosphere, at a temperature of 1500 to 1900° C.
 56. Amethod of producing a titanium carbide-ceramics composite sintered body,comprising the steps of: forming the titanium carbide-ceramics compositepowder obtained by the method as defined in claim 16, into a powdercompact; and sintering said powder compact in a vacuum atmosphere or anitrogen or argon atmosphere, at a temperature of 1500 to 1900° C. 57.The method as defined in claim 23, which further includes the step ofsubjecting said titanium carbide-ceramics composite sintered body to ahot isostatic pressing (HIP) process in a nitrogen or argon atmosphere,at a temperature of 1400 to 1600° C. and a pressure of 50 to 200 MPa.